The present invention is, in general, applicable to replacement of clay tile sewer pipes, concrete pipes, plastic pipes and metal pipes. However, for illustrative purposes, the invention is discussed herein as it applies to replacement of a clay tile sewer pipe.
A typical clay tile sewer pipe is sectioned, each section having an enlarged bell at one end and a tapered portion at the other end. Sections of clay sewer pipe are placed end to end, with the tapered end of each section fitting into the bell end of the proceeding pipe section.
Clay sewer pipes deteriorate over time. Shifting of the ground causes cracking of clay sewer pipes, and tree roots growing into pipe fissures cause further cracking. Settling of the ground may cause pipe joints to pull apart. Clay sewer pipes which become disjointed or which become cracked lose their function and are necessarily replaced. It is, therefore, desirable to provide a means for replacement of clay sewer pipes.
A typical method of replacement of clay sewer pipes comprises the steps of excavation of a trench over the length of the pipe to be replaced, exposing the pipe; extracting the pipe, and replacing the pipe with a new sewer pipe. However, streets, structures, and utility lines lying over a sewer pipe in need of replacement often make excavation of the pipe impracticable. It is, therefore, desirable to provide a means of sewer pipe replacement which does not require disturbance of structures and utilities lying over the pipe to be replaced.
A method of replacing a deteriorated existing sewer pipe without disturbing overlying structures is to slide a flexible plastic replacement pipe through the channel of the existing pipe. However, such methods results in utilization of a replacement pipe whose cross sectional area is substantially less than that of the existing pipe, resulting in reduced carrying capacity. Often it is desirable or necessary to increase, rather than reduce, the carrying capacity of the existing pipe. An increased carrying capacity requires that the diameter of the replacement pipe be greater than the diameter of the existing pipe. It is, therefore, desirable to provide a method for replacing an existing clay sewer pipe with a replacement pipe whose diameter is greater than that of the existing pipe, and without disturbing overlying structures.
It is known that clay sewer pipes may be replaced in situ by means of a driving or pulling machine, such as a pneumatic hammer or a hydraulic ram; such machine being axially aligned with an end of the existing pipe. Axial alignment of such machines requires excavation of a pit at an end of the existing pipe for sub-ground level installation and operation of the machine. The process of excavating a pit at an end of the pipe to be replaced, lowering a machine such as a hydraulic ram or pneumatic hammer into the pit, installation of the machine for operation, removing the machine, and closing the pit after pipe replacement, is an expensive, time consuming and labor intensive process. The process also involves personal safety hazards. Below ground operation of a pneumatic hammer or hydraulic ram exposes the machine operator to a risk of cave in of the walls of the pit. Also, in many instances, ground water will flow into a pit dug for operation of a hammer drill or hydraulic ram, creating a need for dewatering operations. It is, therefore, desirable to provide a pipe replacement system wherein power driven equipment utilized in the process is located above ground.